The article analyzes the original concept of the development of ancient religions and the emergence of Christianity set out in the six-volume work of F.F. Zelinski History of Ancient Religions. Zelnski refutes the well-established idea of the origin of Christianity from Judaism and proves that it was based on the Hellenistic-Roman religion of the early Roman Empire. In this religion, a idea of monotheistic and pantheistic God was formed, which is the basis of all world processes and human actions, at the same time the idea arose of the possibility of a "particle" of God entering a separate human personality (the personality of the emperor). According to Zelinski, it was these ideas that became the basis of Christianity, which radically rethought them, but nevertheless left them close to the beliefs of the majority of the citizens of the Roman Empire; that is why early Christianity quickly spread throughout the empire. The article suggests that Zelinski's flight from Bolshevik Russia in the 1920s and his life in the Polish Catholic environment led to the fact that he refused to develop his ideas to their natural outcome, which could conflict with Catholic teaching. The article reconstructs the result that Zelnski should have come to with the consistent implementation of his ideas: he would have to admit that the teachings of Jesus Christ and early Christianity which arose from the Roman religion and not from Judaism coincides with that religious tradition which the Catholic Church has persecuted in a story called the Gnostic heresy.